KFC – The Krazy Feistel Cipher

Abstract

We introduce KFC, a block cipher based on a three round Feistel scheme. Each of the three round functions has an SPN-like structure for which we can either compute or bound the advantage of the best d-limited adaptive distinguisher, for any value of d. Using results from the decorrelation theory, we extend these results to the whole KFC construction. To the best of our knowledge, KFC is the first practical (in the sense that it can be implemented) block cipher to propose tight security proofs of resistance against large classes of attacks, including most classical cryptanalysis (such as linear and differential cryptanalysis, taking hull effect in consideration in both cases, higher order differential cryptanalysis, the boomerang attack, differential-linear cryptanalysis, and others).